Aircraft with sustaining rotor



Dem-14, 1937. R. H. PREWITT AIRCRAFT WITH SUSTAINING ROTOR 2 Sheets-Sheet 2 Filed March 1l, 1936 a A a 7 J y w m, a o nu w *.17 uw l l/ f ,n l@ m w 6 Q 6 l $3 6 d Y 9 a w; .74 n0 Ha/v 7 4 w I |NvENToR 77 WMM ,1f Vdc ATTORNEYJ vPatented Dec. 14, 1,937

UNITED STATES. PATENT oFFlcE alacaAF'r wrrrnsigamlnanoron I.

Richard n. rrewm, Lansdowne, ra. n lApplication March 11, lese, serial No. sans 9 claims. (ci. n n-,isi

This invention relates to aircraft of the type having a sustaining rotor which constitutes the principal means of control as well as sustension in flight.

One of the chief objects of the invention is the provision of a. simplified mountingl for'the rotor hub providing for tilting of the rotor fore and aft as well as laterally of the craft, to effect flight support or pylon further makes possible sixiipli`y fication ofthe rotor support, and in accordance with this invention a single mast rotor support is contemplated. n

Another object of the invention concerns the disposition of the control elements for the rotor in close proximity to the rotor support, whereby the support of the control elements may all be located within a common sheathing. With reference to this matter, the structure of this invention further provides for disposition of other control elements extended to the rotor hub in close proximity to the single support,'with the same end in view. v,

Another aspect of the invention -is involved in a novel ,bungee or bias system provided for im- 3,-, I posing a bias upon the tiitable rotor, this mechanism being so arrangedA as to utilize theforce not only in the fore and aft plane but also in the lateral plane of tilt.

According rto the invention, independent ad justment means for the longitudinal and lateral bias are provided, these being operative to impose the desired biasin each direction approximately-. independent of Vthe bias in the ot. `r 45 direction.

The invention further contemplates the eniployment of a control stick and novel means coperating therewith for retaining the stick in such position as to maintain the rotor substan- .50 tlally horizontal when the craft is at rest on th'e ground, this with a view to minimizing theeffect of wind at times when" it is not desired that the craft should be air-borne.

How the foregoing, together with other objects IB and advantages as may hereinafter appear, are

' tor.

companying drawings, in which- Flgure 1 is a side view of a rotor hub, support andcontrols arranged in accordance with this invention, a. portion of one blade of the rotor also being shown, as well as a portion of the fuselage in dot-and-dash outline;

Figure 2 is a rear elevational view of the rotor hub and the adjacent part of the support therefor, together with devices embodied in the control system; and

Figure 3 is a view of the control stick for tilting the rotor and also of the bias controls, this view being taken from the rear in Figure 1.

In Figures 1 and 3 the outline of the fuselage attained, will appear more fully as thisidescrip- I tion proceeds, reference being had to the ac' of the craft appears at 4, the numeral 5 indicating fuselage framing elements which are here shown diagrammatically since they form no part of the present invention per se.

The rotor is supported toward the top of a single tubular post, mastor pylon 6 which is fastened to fuselage framing elements within the body-of the craft and extends upwardlytherefrom 'preferably at a slightly rearwardly inclined angle.

It will be observed that the mast 6 extends all the way down tothe lower edge of the fuselage framing. and it should be noted that this mast is fixed to fuselage framing elements at the top as well as at the bottom. thus providing xation at materially spaced points, above which' the single post extends to provide cantilever support for the ro V Toward its upper end the post 6 carries a yoke comprising a pair of curved members 1-1 which embrace the hub unit generally designated v "by the letter A. The hub unit incorporates an of a single spring or other yielding device for bias external casing a housing a rotor spindle, bearings, etc., the details of which need not be fully described herein. Then rotor spindle projects above the casing! and carries pairs of apertured lugs l towhich links i0 are pivoted, as by horizontal pivots Il.` Each link lli (only one being shown in the drawings) is in turn pivoted to the forkiittlng I2 by a drag articulation such as the substantially vertical pivot I3. The blade fork .i2 is' secured to the spar i4 which in turn carries the blade proper I5. v

From the above it will be seen that the individual blades of the rotor (3 being incorporated in the form shown) are each free to apwabout the substantially horizontal pivot Il under the iniluence of night forces, and also to move fore 'and aft in` its general path of travel about the drag articulation I3. Each blade may be supit is not rotating at ight speeds, by a pin I6 set into the extension link I0 and cooperating with abutments |1 formed on the attachment ears 9. Excessive upward swinging of each blade may similarly be prevented by a stop I8 formed on ea'ch ear 9. V v

For purposes of control of the craft in flight, the rotor hub unit is mounted for tilting movement both fore and aft as well as laterally, so as to accomplish control in the general manner disclosed in application Serial No. 645,985, led December 6, 1932, of Juan de la Cierva.

In accordance with the present invention, the structure providing for such tilting of the hub and the rotor includes a yoke I9 substantially horizontally embracing an upper part of the hub unit and pivotally joined by pins 2|) at its ends with the upper ends of the yoke parts 1-1 projecting from the fixed pylori 6. The hub unit is carried on yoke I9 by means of a single trunnion 2|, and the two trunnions 20 and 2| thus provide freedom for tilting movement of the rotor hub and the rotoras a whole both fore and aft as well as laterally of the craft. For reasons which are more fully set out in the copending application of Juan de la Cierva referred to above, the longitudinal tilting trunnion 2U is forwardly offset from the rotor axis, as seen in Figure 1, while the lateral trunnion 2| is offset from the rotor axis to the left when viewed from the rear as in Figure 2. The oiset of the lateral. tilting axis just referred to is proper for a rotor turning in a counterclockwise direction when viewed in top plan. The purposes of offsetting the tilting axes, and the degree of offset, are fully discussed in the aforementioned copending application of Juan de la Cierva and need not be considered in detail herein since they form n'o part of the present invention per se.

In addition to the devices and elements referred to above, the hub unit A preferably incorporates gearing including a ring gear and a pinion, the latter of which is adapted to be driven by the torque shaft 39 which, it will be seen, extends downwardly toward the body of the craft closely adjacent to the post 6. 'I'his shaft further is provided With exible joints, including a universal joint 40, for the purpose of accommodating tilting movements of the hub and rotor.

The control system of this invention further includes at least one control stick 22 (a dual 23 being provided, if desired) which is pivotally mounted on the torque tube 24 at 25, this pivot providing freedom for fore and aft movement of the stick 22. The tube 24 is suitably mounted in bearings -26 and the lower swinging end of the stick 22 is joined by a compression element 21 with the lower end of stick 23, which in turn is coupled by link 28 with arm 29 of a bellcrank pivoted at 30 and having its other arm3l joined by a push-and-pull rod 32 with arm 33 of an additional bellcrank. This latter crank is pivoted at 34 to the pylon post 6 and has an arm 35 to which the link 36 is attached, link 36 in turn being pivoted at 31 to a device 38 which is rigid with the yoke I9.

The connections just described provide for fore and aft tilting of the rotor upon fore and aft movement of the control stick 22 as suggested by the dot-and-dash positions 22a and 22h.

Lateral tilting of the hub and rotor is accomplished by lateral displacement of the control stick 22, as suggested by the dot-and-dash positions 22o and 22d in Figure 3. This movement rotates the torque tube 24 and thus also swings the arms 4|-4|. A controlcable 42 extends laterally from the arms 4| to the rotor hub in a closed circuit which may be traced, as follows. Proceeding toward the left in Figure 3 and thence toward the left in Figure 1, the cable 42 iirst passes over a pulley 43 and thence forwardly to a pulley 44 from which it extends upwardly along the post 6 to a pulley 45. From this point the cable extends upwardly and takes a U turnl a bellcrank which is pivoted to the fixed pylon support at 50 and which has an additional arm 5I projecting laterally for pivotal attachment to the link 52. Link 52 in turn is jointed at its upper end to the arm 53 whichis carried by the housing of the hub unit and projects rearwardly and thence laterally out of the open side of yoke I9.

Lateral movement of the control stick thus effects lateral tilting of the hub and rotor about the trunnion 2|.

Stops for limiting longitudinal and lateral movement of the control stick are also provided in accordance with this invention. The longitudinal stop includes an abutment 54 carried on the torque tube 24 by braces 55. Upon longitudinal movement of the stick 22 the tube 21 moves with respect to the stop 54 and on the tube 21 are provided a pair 'of spaced cooperating stops 56. These may be set so as to permit the desired rangeof movement but limit movement to that range.

Limitation of the lateral movement is accomplished by a pair of arms 51 (see Figure 3) radiating from the torque tube 24 and carrying abutments in the nature of wood blocks or the like which may be out to a desired thickness, as shown at 58. Theseblocks may be positioned to contact with any fixed part of the body such as the transverse fuselage brace 59.

With regard to the controls described above. attention is directed to several important advantages flowing therefrom, as follows.

In the first place, all of the control connections -lie close to the single pylon post 6 and thus permit effective streamlining of the parts as by enclosure within a. single shell indicated at 6a.

More important, however, is the advantage flowing from the arrangement of the operating parts in a manner which eliminates or at least substantially reduces bending loads in-the pylon. Note particularly that in accordance with this invention provision is made for shifting the lift line of the rotor for control purposes and that the operating elements for controlling the shifting are mounted or pivoted on the single mast, preferably closely adjacent to the hub itself, from which region connections extend downwardly to the body in close proximity to the axis of the rotor support. Note also that these control elements all act in planes paralleling the axis of the support or single post. These factors are important in minimizing undesired stresses of the type above referred to.

In accordance with this invention, provision is also made for imposing a bias on the longitudinal and lateral controls. Thisbias or bungee sys tem incorporates a main bias spring 88, one end of which is coupled by a cable 6I passing over pulleys 62 and 63 with a tting 84 (see Figure 2) which in turn is pivotaily mounted at 8l on link 66 universally jointed as at. 61 to a ange or.web 68 carried on the hub casing.' From Figure 1 it will be seen that the point of attachment of cable 6I to the .web 69 lies to the rear of the trunnion for longitudinal tilting, and in view of this the force of spring 68 tends to tilt the rotor `upwardly at the front.. The amount of this bias may be controlled by anchoring spring 66 to an adjustable device including cable 89 passing over pulley 18 for connection with arm 1I fixed on the lever 12.

Lever 12 is adapted to engagey stops on the quadrant 13 for purposes of adjustment. In order to approximately balance the force of spring` and thus facilitate movement of the control lever 12, this lever,'which is pivotaily mounted at 1l, has a lower extension 19 to which cable'16 is attached, the latter passing over pulley 11' connected to one end of spring 18, the other end of which may be fastened to any suitable fixed point.

A lateral bias eect is securecl'"=by lateral` displacement of the fitting 6l (see vFigure 2), this being accomplished by a closed circuit cable 19, the ends of which are fastened to the iltting 64 at opposite sides thereof as clearly' shown in Figure 2. From the fitting 64 the cable extends laterally in both directions to pass over pulleys -88 and thence over pulleys 8l, downwardly along the pylon post ,6 to a point adjacent the upper side ofthe fuselage, at which pulleys 82 and 83 serve to guide each run of the cable 19 laterally outwardly and then rearwardly to pass over additional pulleys 84. Afterl this the two runs of the cable join and thus complete the circuit.

' For the purpose of moving cable 19 back and forth and thus controlling the lateral bungee effect, an arm 85 is secured thereto and mounted on shaft 86 which carriesworm wheel 81 meshing with the worm 88 adapted to be rotated by the operating handle 89.

natation of the handle ss thus dispiaces the' fitting 64 (see Figure 2). Assuming a displacement tothe left in Figure 2; it will be seen that y the lefiect of the bias spring 68 will have a lateral component operating about the trunnion 2|. In this way a single bungee device serves' for both longitudinal and lateral bias enact.

In considering -the operation of. the bungee system, it is first pointed out. that ordinarily a heavier load or bias is required in the longitudinal plane than Yin the lateral plane.v The ar.

rangement of the.l present invention meets this situation nicely, it being pointed out that a relatively heavy longitudinal bias maybe secured by adjustment of the lever 12 to cause spring 60 toimpose a, relatively heavy load on cable 6I. This loading, it will be noted, may be obtained regardless of the adjustment of the bias in the lateral plane, i. e., it may be obtained with adjustments of the lateral bias giving a substantial force or giving zero force in the lateral plane. Thus, even though the bias effect is derived from a single device, the loading and adjustments in the twovdiiferent planes are in large part independent of each other.

A `further feature vof'the invention concerns provision for retaining Athe control stick in a given position when the craft is at rest'on the ground. This mechanism comprises a socket 98 adapted to receive plunger 8| which is mounted at the upper end of the controll stick 22. This socket may conveniently be supported from other fuselage members by bracing elements 92 and divergent or haring flanges 98 are preferably employed for the purpose of guiding the control stick into the socket.

The plunger 9| is normally urgedupwardly by means of a spring 94, although it may be displaced downwardly by the pin which projects laterally 'from the control stick. The pin, ofl

course, is pressed down when it is desired to. re-

lease. the control stick, although the shape of the lifting the machine when it is the intention to remain on the ground.

l. In an aircraft having a sustaining rotor, a pylon structure for supporting the rotor, a hub support pivotaily mounted on the pylon, a non-.rotative hub part pivotaily mounted on said support, the axes of the two pivotal mountings being angledv with respect to each other so as to provide for tilting of the hub in all directions, and mechanism lfor controlling tilting of -the hub including a lever pivoted intermediate its ends on the pylon adjacent the mounting of the hub thereon, a short push-pull member interconnecting one end of said lever and said nonmediate its ends on the pylon adjacent the mounting of the hub thereon, a second short push-pull-member interconnecting one end of the second lever and said hub support, and means for actuating the other ends of both of said levers lincluding for at least one of said levers a flexible cable connected therewith and extended downwardly for operation by an operator in the body of the craft, whereby a major portion of rotative hub part, a second lever pivoted inter-v the load imposed in the push-pull member is carried in the pylon,l thereby relieving the conv trol means of a major portion of said fload.

2. In an aircraft having a sustaining rotor, a rotor hub mounted for tilting movements in all directions to vary the position of the lift-line of the rotor, a non-rotative element tiltably movable with the rotor hub, a bungee spring anchored at one end, to a fixed part of the craft,

and means interconnecting the other end of said spring and said element including a tension-connection transmitting the spring force to said element in one direction and another connection transmitting the spring force to said element in a direction substantially transverse the first direction.

3. In an aircraft having va sustaining rotor, a rotor hub mounted for tiltingmovements in all directions to vary'the position of the. lift-line of the rotor, ua. non-rotative element tiltably movable with the rotor hub, a bungee spring anchored at' one end to a xed partv of the craft, and means interconnecting the other end of said spring and said elementA 'including a tension connection transmitting the spring force to said element in one direction and another connection transmitting the spring force to said element inA a direction substantially transverse the .first direction, and controllable means for adjusting the bungee eiect transmitted to said element movable with the rotor through said two connections.

4. In an aircraft having a sustaining rotor, a rotor hub mounted for tilting movements in al directions to Vary the position of the lift-line 0f the rotor, a non-rotative element tiltably movable with they rotor hub, a bungee spring anchored at one end to a xed part of the craft, and means interconnecting the other end of said spring and said element including a tension connection transmitting the spring force to ysaid element in one direction and another connection transmitting the spring force to said element in a direction substantially transversethe iirst direction,

and controllable means for adjusting the bungee effect transmitted to said element movable with the rotor through said two connections, said controllable means being associated with the said two connections and providing for substantially independent adjustment' of the bungee eifect trans-l fixed part of the craft including a second spring `iixed at one end to a xed part of the craft and an adjustable tension connection between the tw springs.

6. In an aircraft having a sustaining rotor, a

mounting structure for the rotor including a tu- .bular cantilever pylon member lying in the longitudinal plane of symmetry and inclined upwardly and rearwardly, a generally semi-circular yoke attached intermediate its ends to the top of the pylon member and lying in a transverse plane, pivot means associated with the prongs of said yoke, a second yoke lying in a generally horizon tal plane and pivotally mounted-at its ends on said pivotI means, anda non-rotative rotor hub part pivotally mounted within the second yoke intermediate the ends thereof in position to definey a generally upright rotor axis rearwardly offset from the axis of said pivot means,`the second yoke surrounding the forward portion of the hub part.

'7. In an aircraft having a Sustaining rotor, a

rotor mount projecting upwardly from the mainy body structure of the craft and including an uppivotally mounted within the second yoke inter- Y mediate the ends thereof in position to define a generally upright rotor axis rearwardly offset from the axis of said pivot means, the second yoke surrounding the forward portion of the hub, and means for controllably tilting the rotor hub including a control connection extended away from said non-rotative hub part rearwardly of the second yoke substantially in the plane thereof.

l8. In an aircraft having a sustaining rotor, a rotor mount projecting upwardly from the main body structure of the craft and including an up wardly open yoke lying in a transverse plane, pivot means associated with the prongs of said yoke, an open-sided yoke lying in a generally hori zontal plane and pivotally mounted at its ends on said pivot means, a non-rotative rotor hub part pivotally mounted within the second yoke intermediate the ends thereof in position to denne asurrounding the forward portion of the hub, and

means for controllably tilting the rotor hub including a control connection extended away from said non-rotative hub part rearwardly of the second yoke substantially in the plane thereof, the means for controllably tilting the hub further iny cluding a lever pivotally mounted on the rotor mount closely adjacent to the hub, a push-pull element interconnecting one arm of said lever and said connection, and a flexible actuating cable connected with another arm of said lever at a distance from its pivotal mounting greater than the distance between the pivotal mounting of the lever and the point of connection of said pushpull element with said lever.

9. In an aircraft having a sustaining rotor with flappingly pivoted blades, a pylon structure for -supporting the rotor, a hub support pivotally mounted on the pylon, a non-rotative hub part -pivotally mounted on said support, the axes of the two pivotal' mountings being angled with respect to each other so as to provide for tilting of the hub in all directions, and mechanism for controlling tilting of the hub including a lever plvoted intermediate its ends on the pylon adjacent the mounting of the hub thereon, a short push-pull member interconnecting one end of said lever and a part tiltable with the rotor hub, and a flexible control cable connected with the other end of said lever and extended downwardly for actuation by an operator in the body of the craft, the two ends of said lever being proportioned to reduce the load in the control cable as compared with the load in the push-pull member, whereby a major portion of the control and blade flapping loads imposed on the push-pull member are carried in the pylon,

thereby relieving the control cable of a major portion `of said load.

RICHARD H. PREWI'I'I. 

